Reliability of torque measurements during passive isokinetic knee movements in healthy subjects

In the literature, few data are available about the reliability of torque measured during passive isokinetic knee movements. This study investigated the consistency of torque measurements during passive knee movements at 60, 180 and 300 degrees/second in 30 healthy subjects. Intraclass correlation values ranged between 0.78 and 0.92 when the results of two consecutive tests were compared. When retests were performed after repositioning the subjects, intraclass correlation values ranged between 0.43 and 0.87. These findings indicate the necessity for meticulous standardization of the test situation. Series of 10 consecutive movements, specifically repetitions of knee flexion at 180 and 300 degrees/second, indicated that torque measurements during the first two movements were less stable than those following. A concurrent change in electromyographic activity in the rectus femoris muscle suggested that these torque variations resulted from habituation of the stretch reflex.     

Effect of stabilization on maximal isokinetic torque of the quadriceps femoris muscle during concentric and eccentric contractions

The purpose of this study was to investigate the effect of stabilization on the maximal isokinetic torque generated by the quadriceps femoris muscle during concentric and eccentric contractions at different velocities using the KIN/COM isokinetic dynamometer. Fifteen female volunteers between the ages of 18 and 32 years were trained to perform maximal isokinetic concentric and eccentric contractions. Each subject participated in two testing sessions. In one testing session, subjects were stabilized maximally, and in the other testing session, subjects were stabilized minimally. Subjects were tested both concentrically and eccentrically at velocities of 30 degrees, 60 degrees, 90 degrees, 120 degrees, 150 degrees, 180 degrees, and 200 degrees/sec. The velocity sequence and stabilization procedure used were randomly assigned. Two nested model analyses of variance followed by post hoc comparisons were used to analyze the data. Results revealed no significant difference between the maximal stabilization procedure and the minimal stabilization procedure for concentric and eccentric contractions. The results of this study should aid rehabilitation specialists in the development of testing and rehabilitation procedures when using the KIN/COM.     

Effects of Russian current and low-frequency pulsed current on discomfort level and current amplitude at 10% maximal knee extensor torque

Background: Low-frequency pulsed current (LFPC) and Russian current (RC), a type of kilohertz-frequency alternating current, have been frequently used for muscle strengthening in rehabilitation programs. Despite the popularity of these current types, it is unclear which is most effectively able to generate a similar submaximal torque with minimal discomfort and current amplitude. Objective: To compare discomfort and current amplitude between LFPC and RC to achieve a knee extensor torque of 10% of the maximal isometric voluntary contraction (MIVC). Methods: Twenty-two healthy subjects were subjected to three electrically elicited knee extensor submaximal contractions (10% MIVC) that were sustained for 10 seconds. The current amplitude required to achieve 10% MIVC and subjective discomfort were assessed directly by the electrical stimulator and with the Visual Analogue Pain Scale, respectively. A paired t-test was used to determine differences between the electrical currents (α?=?0.05). Results: LFPC required significantly lower current amplitude (15%) and a lower discomfort level (50%) to achieve 10% of MIVC compared to RC. Conclusion: LFPC current seems to be more effective than RC with respect to discomfort level and current amplitude to produce 10% of MIVC.     

Complexity of knee extensor torque in patients with frailty syndrome: a cross-sectional study

BackgroundFrailty syndrome is characterized by a marked reduction in physiological reserves and a clinical state of vulnerability to stress. Torque complexity analysis could reveal changes in the musculoskeletal systems that are the result of having the syndrome.ObjectiveThe aim of this study was to evaluate the complexity of submaximal isometric knee extensor torque in frail, pre-frail, and non-frail older adults. A secondary aim was to analyze the torque complexity behavior in different force levels in each group.MethodsA cross-sectional study was conducted. Forty-two older adults were divided into three groups: non-frail (n = 15), pre-frail (n = 15), and frail (n = 12). The data collected included body composition, five times sit-to-stand test, walking speed, and isometric knee extensor torque at 15, 30, and 40% of maximal voluntary contraction. The knee extensor torque variability was evaluated by coefficient of variation, and the torque complexity was evaluated by approximate entropy and sample entropy.ResultsThe frail group presented a reduction in body mass and peak torque value compared to the non-frail group. Also, the frail group showed worse physical performance (on the five times sit-to-stand test and walking speed) compared to the pre-frail and non-frail groups. In addition, the frail older adults showed reduced torque complexity compared to the non-frail group. Finally, the association between torque complexity and force levels remained similar in all groups.ConclusionTorque complexity is reduced in the presence of frailty syndrome.     

Excitability of spinal motor neurons during motor imagery of thenar muscle activity under maximal voluntary contractions of 50% and 100%

[Purpose] We often perform physical therapy using motor imagery of muscle contraction to improve motor function for healthy subjects and central nerve disorders. This study aimed to determine the differences in the excitability of spinal motor neurons during motor imagery of a muscle contraction at different contraction strengths. [Subjects] We recorded the F-wave in 15 healthy subjects. [Methods] In resting trial, the muscle was relaxed during F-wave recording. For motor imagery trial, subjects were instructed to imagine maximal voluntary contractions of 50% and 100% while holding the sensor of a pinch meter, and F-waves were recorded for each contraction. The F-wave was recorded immediately after motor imagery. [Results] Persistence and F/M amplitude ratio during motor imagery under maximal voluntary contractions of 50% and 100% were significantly higher than that at rest. In addition, the relative values of persistence, F/M amplitude ratio, and latency were similar during motor imagery under the two muscle contraction strengths. [Conclusion] Motor imagery under maximal voluntary contractions of 50% and 100% can increase the excitability of spinal motor neurons. Differences in the imagined muscle contraction strengths are not involved in changes in the excitability of spinal motor neurons.Key words: Motor imagery, F-wave, Muscle contraction strength     

Reliability of knee flexor peak torque measurements from a standardized test protocol on a Kin/Com dynamometer.

The test-retest reliability of a specific test protocol for the measurement of peak torque of the knee flexors using a Kin/Com dynamometer was evaluated. The maximum voluntary torque generated by the left knee flexors during constant velocity resisted-muscle shortening (RMS) and muscle lengthening (RML) was measured in a sitting position in 11 healthy women with no history of knee pathology. Each subject performed two tests at each of two velocities (30 degrees/sec and 180 degrees/sec) in a single session. All subjects repeated these four tests one week later. A test consisted of four complete RMS/RML cycles through a range of 65 degrees. The peak torque generated from each test was used to measure test-retest reliability. All data were gravity compensated. Intraclass correlation coefficients (ICCs) were calculated from ANOVA tests for RML and RMS at both velocities. The within sessions ICCs ranged from .94 to .98 for 30 degrees/sec and from .92 to .97 at 180 degrees/sec. The ICCs between sessions were generally lower and ranged from .79 to .90 for 30 degrees/sec, and from .75 to .88 for 180 degrees/sec. It is concluded that using these test protocols, peak torques for both RMS and RML can be measured with a high degree of reliability at two commonly used velocities.     

Towards an acoustic model-based poroelastic imaging method: II. experimental investigation

Soft biological tissue contains mobile fluid. The volume fraction of this fluid and the ease with which it may be displaced through the tissue could be of diagnostic significance and may also have consequences for the validity with which strain images can be interpreted according to the traditional idealizations of elastography. In a previous paper, under the assumption of frictionless boundary conditions, the spatio-temporal behavior of the strain field inside a compressed cylindrical poroelastic sample was predicted (Berry et al. 2006). In this current paper, experimental evidence is provided to confirm these predictions. Finite element modeling was first used to extend the previous predictions to allow for the existence of contact friction between the sample and the compressor plates. Elastographic techniques were then applied to image the time-evolution of the strain inside cylindrical samples of tofu (a suitable poroelastic material) during sustained unconfined compression. The observed experimental strain behavior was found to be consistent with the theoretical predictions. In particular, every sample studied confirmed that reduced values of radial strain advance with time from the curved cylindrical surface inwards towards the axis of symmetry. Furthermore, by fitting the predictions of an analytical model to a time sequence of strain images, parametric images of two quantities, each related to one or more of three poroelastic material constants were produced. The two parametric images depicted the Poisson's ratio (nu(s)) of the solid matrix and the product of the aggregate modulus (H(A)) of the solid matrix with the permeability (k) of the solid matrix to the pore fluid. The means of the pixel values in these images, nu(s) = 0.088 (standard deviation 0.023) and H(A)k = 1.449 (standard deviation 0.269) x 10(-7) m(2) s(-1), were in agreement with values derived from previously published data for tofu (Righetti et al. 2005). The results provide the first experimental detection of the fluid-flow-induced characteristic diffusion-like behavior of the strain in a compressed poroelastic material and allow parameters related to the above material constants to be determined. We conclude that it may eventually be possible to use strain data to detect and measure characteristics of diffusely distributed mobile fluid in tissue spaces that are too small to be imaged directly.     

Abdominal weight and inspiratory resistance: their immediate effects on inspiratory muscle functions during maximal voluntary breathing in chronic tetraplegic patients.

OBJECTIVE: To study the immediate effects of maximal voluntary (MV) breathing, with and without abdominal weight (AW) or inspiratory resistance (IR), on inspiratory muscle functions in chronic tetraplegic patients. DESIGN: A crossover trial design. SETTING: Rehabilitation department of a university hospital. PARTICIPANTS: Nine tetraplegic men injured at the C4 to T1 levels, with a mean duration of injury of 72.8 months. INTERVENTIONS: Each subject performed MV breathing without and with AW load (AWMV breathing) and IR load (IRMV breathing) separately. MAIN OUTCOME MEASURES: Electromyographic (EMG) activity of the inspiratory muscles, mouth pressure, inspiratory flow, and inspiratory volume. RESULTS: AWMV breathing evoked greater diaphragmatic EMG activity, inspiratory flow, and inspiratory volume than did IRMV breathing, although the increase of diaphragmatic EMG activity was not statistically significant. Conversely, IRMV breathing produced greater sternocleidomastoid EMG activity and negative mouth pressure than did AWMV breathing. Both AWMV and IRMV breathing evoked greater inspiratory muscle EMG activity than did MV breathing. CONCLUSION: AW and IR loads have differential immediate effects on the inspiratory muscle functions during MV breathing in patients with chronic tetraplegia, suggesting that these two breathing maneuvers may have dissimilar mechanisms of training in such patients. The muscle EMG activity evoked during MV breathing with AW or IR is greater than that without a mechanical load, implying that mechanically loaded training in tetraplegic patients results in load compensatory adjustments via their respiratory motor output to improve respiratory function.     

The effects of failing to control pain: an experimental investigation

Chronic pain patients are often confronted with repeated failure to achieve pain relief. The aim of this study was to experimentally investigate the effects of repeated failing attempts to control pain on pain impact (pain intensity, emotional and physiological responses). Perceived control over an electrocutaneous pain stimulus was manipulated between subjects by success or failure feedback on a task by which control over pain could be acquired. In addition, success or failure at the task was manipulated without suggesting a possibility to control pain. It was hypothesized that successful control would lead to lowest pain impact, whereas failure to control pain would lead to even higher pain impact than absent control. Furthermore, it was hypothesized that failure feedback would increase pain impact when compared to success feedback. Results indicated that repeated failure to control pain increased anger and heart rate responses compared to the other conditions, but not pain intensity. It is concluded that persistent efforts to control pain in the face of failure may lead to the maintenance or exacerbation of physiological and emotional responses.     

Variability of symphysis-fundus height measurements: an experimental study among general practitioners

With the aim of evaluating the impact of supervised training during a postgraduate course in obstetrics and gynaecology, the variability of symphysis-fundus (SF) height measurements was studied by a group of general practitioners (GPs), all of whom provided primary antenatal care. A nested analysis of variance was used. The SF height measurements of the group differed significantly from those of a senior obstetrician and the course training had no impact on the variability. Similar studies should evaluate measurement variability in the light of pregnancy outcome.     

Provider reliability with interventions for knee impairments: a preliminary investigation to facilitate development of an MDT-based knee intervention taxonomy

Objectives: The lack of a standardized intervention taxonomy in comparative effectiveness research trials has led to uncertainty regarding the management of individuals with knee impairments. Inconsistently and poorly defined interventions affect frontline–care providers’ abilities to understand and assimilate research findings into practice. An intervention taxonomy could help overcome the lack of treatment specificity commonly found in research trials.

Methods: In the present study, we aimed to develop a Mechanical Diagnosis and Therapy (MDT)–based taxonomy and test the levels of reliability between providers who currently manage individuals with knee impairments in a rehabilitation setting. A total of 182 participants accessed the study during the study period, in which 180 consented to participate and 59 completed the survey (98.9% participation rate; 32.7% completion rate).

Results: A total of 89.8% of the participants who completed the survey were physical therapists. Fleiss kappa values for the primary, secondary, and tertiary categories were 0.90, 0.89, and 0.71, respectively. The results of our investigation suggest substantial to almost perfect levels of reliability for identifying diverse MDT-based knee interventions displayed in video and vignette format within a sample population primarily of physical therapists who currently manage individuals with knee impairments in a rehabilitation setting.

Discussion: Our findings show acceptable levels of reliability and provide support for using this standardized MDT-based intervention taxonomy as a way to improve intervention specificity and generalizability in comparative effectiveness research.

Level of Evidence: 5     

The interruptive effect of pain in a multitask environment: an experimental investigation

Daily life is characterized by the need to stop, start, repeat, and switch between multiple tasks. Here, we experimentally investigate the effects of pain, and its anticipation, in a multitask environment. Using a task-switching paradigm, participants repeated and switched between 3 tasks, of which 1 predicted the possible occurrence of pain. Half of the participants received low intensity pain (N = 30), and half high intensity pain (N = 30). Results showed that pain interferes with the performance of a simultaneous task, independent of the pain intensity. Furthermore, pain interferes with the performance on a subsequent task. These effects are stronger with high intensity pain than with low intensity pain. Finally, and of particular importance in this study, interference of pain on a subsequent task was larger when participants switched to another task than when participants repeated the same task. PERSPECTIVE: This article is concerned with the interruptive effect of pain on people's task performance by using an adapted task-switching paradigm. This adapted paradigm may offer unique possibilities to investigate how pain interferes with task performance while people repeat and switch between multiple tasks in a multitask environment.     

The validity of an intravenous isotope method for cerebral blood flow measurements. An experimental study.

The intravenous isotope method has been examined. The method uses 99Tc as the indicator with recording of the radioactivity with two gamma-dectors placed bilaterally over the skull and oriented over the bifurcation of the middle cerebral artery. 65% of the total curve obtained was found to be generated by activity passing in the ipsilateral internal carotid artery, 25% in the contralateral internal carotid artery and less than 10% by activity passing in the two external carotid arteries. The counting rate efficiency for an intracerebral location was 19.4 +/- 1.8 times the count rate from the same activity placed at 1 m distance in air which in turn was 5 cps/muCi. The variability in efficiency from patient to patient was thus estimated at +/- 9%. The duration of the input bolus had a marked influence on the vurve, which will be of importance since it showed a rather large variability from patient. Using the peak activity as an index of the cerebral blood flow the intravenous method showed a surprisingly good correlation with the 133Xe wash-out method; the correlation coefficient was 0.93 and the variability at slightly subnormal values estimated at +/- 15%. It is concluded that the method can be used in the case of limited demands on the accuracy of the cerebral blood flow determinations.     

Knee rotational laxity: an investigation of bilateral asymmetry for comparison with the contralateral uninjured knee

Background

Instability associated with anterior cruciate ligament injury is commonly evaluated against the patient's contralateral knee. The objectives of this study were, therefore, to assess symmetry of rotational knee laxity in vivo under passive torsional loading in uninjured subjects, and to compare mean rotation of this control group with the contralateral, intact knees of anterior cruciate ligament deficient patients.

Methods

Axial knee rotation was measured in 29 patients with unilateral anterior cruciate ligament injury and 15 uninjured age and gender-matched control subjects using an imaging-compatible torsional loading device. Side-to-side differences in internal, external, and range of knee rotation were assessed in the control group and mean bilateral knee rotation was compared to the patients' contralateral knee data at both full extension and 30° of flexion.

Findings

Statistically significant differences in symmetry were found in three of the six measures of transverse plane rotation in the uninjured knees; a mean side-to-side difference of 2.2° in range of rotation was detected in the flexed position. No significant differences were observed between the mean values of the healthy control group and the contralateral knees of the anterior cruciate ligament deficient patients.

Interpretation

Bilateral asymmetry of rotational laxity occurs in healthy individuals. Nevertheless, comparability of rotational knee laxity between the contralateral limbs of patients and the uninjured population was evidence that rotational laxity was not inherent or developed in the contralateral knees of the anterior cruciate ligament deficient participants.     

beta-Lactamase produced by a highly beta-lactam-resistant strain of Bacteroides fragilis: an obstacle to the chemotherapy of experimental mixed infections.

A strain of Bacteroides fragilis, which produces a metallo-beta-lactamase, was inoculated into pouches on the backs of rats together with a beta-lactamase-negative Escherichia coli highly sensitive to beta-lactam antibiotics. The mixed infection rat pouch model was treated with either flomoxef (susceptible to hydrolysis by the beta-lactamase produced by B. fragilis), or cefmetazole (relatively resistant to hydrolysis). In this model of mixed infection flomoxef showed weak in-vivo activity against E. coli, although showing the same strong activity in a model of single infection with E. coli. On the other hand, cefmetazole showed strong activity against E. coli, even in the model of mixed infection. The concentrations of both drugs in the pouches were decreased in infections with the strain of B. fragilis. There was a greater decrease in the concentration of flomoxef than of cefmetazole. Flomoxef was unstable whereas cefmetazole was relatively stable in the pouch exudates that had been infected with B. fragilis. These experimental data suggest that bacteria that produce a metallo-beta-lactamase decrease the in-vivo efficacy of beta-lactam antibiotics against other co-infecting bacteria. Thus, it is suggested that it is important in the chemotherapy of mixed bacterial infections that include these highly resistant beta-lactamase-producing bacteria to use antibiotics that are stable to hydrolysis by these enzymes.     

常规拔牙病人艾滋病病毒污染情况调查及防护

目的:对常规拔牙术中艾滋病病毒污染情况进行调查,进一步控制医源性感染。方法:随机抽取200例门诊拔牙病人的术中止血棉球,浸入盛有1ml生理盐水的无菌试管内,其浸出液用3种方法进行艾滋病病毒检测。结果:200例标本中查出1例HIV抗体阳性(0.5%)。结论:迫切要求口腔医务工作者要加强职业防护,有效防止艾滋病通过口腔科诊疗传播。     

Discriminative stimuli produced by clonidine: an investigation of the possible relationship to adrenoceptor stimulation and hypotension

In a leverpressing operant procedure, male rats were trained to respond for food reinforcement on one lever after an injection of clonidine (0.04 mg/kg) and to respond on an alternate lever for food reinforcement after an injection of saline. All 36 rats learned to discriminate the drug reliably from saline, thereby indicating that clonidine produces discriminative interoceptive stimuli. The discriminative stimulus was both dose- and time-dependent, with an ED50 of 0.018 mg/kg and an optimum time of action occurring from 15 to 60 min after injection. Although clonidine produced a reduction in response rate, this was not the basis of the discriminative stimulus as other drugs with similar depressant action did not generalize. The clonidine stimulus was dose-dependently antagonized by the alpha-2 adrenergic antagonist, yohimbine, whereas receptor antagonists of alpha-1 adrenergic, beta adrenergic, dopaminergic, serotonergic, cholinergic or opioid systems were ineffective in blocking the interoceptive stimulus produced by clonidine Lofexidine, guanabenz and methyldopa, all centrally acting hypotensive drugs that act through alpha-2 adrenoceptor mechanisms dose-dependently generalized to the clonidine cue, whereas hydralazine, minoxidil, propranolol and prazosin, hypotensive drugs acting through other mechanisms, did not generalize. These results suggest that clonidine produces interoceptive stimuli that are discriminable by rats and mediated through central alpha-2 adrenoceptor stimulation.     

Fear of movement/(re)injury and muscular reactivity in chronic low back pain patients: an experimental investigation.

This experiment was set up to test the hypothesis that confrontation with feared movements would lead to symptom-specific muscular reactivity in chronic low back pain patients who report high fear of movement/(re)injury. Thirty-one chronic low back pain patients were asked to watch a neutral nature documentary, followed by a fear-eliciting video-presentation, while surface electromyography (EMG) recordings were made from the lower paraspinal and the tibialis anterior muscles. It was further hypothesized that negative affectivity (NA) would moderate the effects of fear on symptom-specific muscular reactivity, as well as the effects of muscular reactivity on pain report. The results were partly as predicted. Unexpectedly, paraspinal EMG-readings decreased during video-exposure but this decrement tended to be less in fearful patients than in the non-fearful patients. Negative affectivity did not moderate this effect, but moderated the effect of pain-related fear on muscular reactivity of lower leg muscles. In addition, NA directly predicted muscular reactivity in the right tibialis anterior muscle. As predicted, there was a significant covariation between left paralumbar muscular activity and pain report. This association was moderated by NA, but in the opposite direction. The findings extend the symptom-specificity model of psychophysiological reactivity, and support the idea that pain-related fear perpetuates pain and pain disability through muscular reactivity.